Many Happy Returns

Two years have passed since Sherlock Holmes's apparent death, and London has more or less learned to live without him. John Watson and DI Lestrade are getting on with it, each in his own way. Anderson is not getting on with it. Where everyone else has accepted the obvious, he stays certain that Holmes is alive, and he keeps saying so.

The episode gives his obsession something to feed on. A series of seemingly unconnected crimes, stretching from Tibet through India to Germany, begins to surface, and Anderson insists the pattern means something. The cases are laid out piece by piece, and each one reads like a question: what would the missing detective make of this?

But the real subject is absence. John has Mary Morstan in his life now, and a version of ordinary that Holmes would find unbearable. Lestrade has his job. The city has moved on. Only Anderson holds the door open, and the episode is quietly kind to him for it.

Mark Gatiss and Steven Moffat wrote it, Jeremy Lovering directed, and the small cast does exactly what a short piece needs: Benedict Cumberbatch and Martin Freeman as Holmes and Watson, Rupert Graves as Lestrade, Amanda Abbington as Mary, Jonathan Aris as Anderson, Louise Brealey as Molly Hooper, with George Appleby's Small Thief, Laura Dale's Beautiful Drug Dealer and a reporter played by Jason Thomas Brown keeping the edges busy. It aired on Christmas Day 2013, which is the right day for this kind of gift.

It is a strange little object, part teaser and part memorial, and it was always going to be a hard sell for anyone who wanted a proper case. The show gambles that its audience cares more about the people left behind than about the puzzle, and for the most part the gamble pays off. And for anyone who had spent two years refusing to believe the obvious, the whole thing reads as a promise: he'll be back.